A green strategy for co-production of xylooligosaccharides and fermentable sugars from birch via tween-assisted tartaric acid pretreatment

Abstract

Developing a clean, efficient, and economically viable pretreatment strategy that enables the co-production of xylooligosaccharides (XOS) and fermentable sugars from woody biomass remains a major challenge in sustainable biorefinery. Although hydrothermal and dilute organic acid pretreatments are effective for XOS production, their ability to enhance subsequent enzymatic hydrolysis is often limited. Post- delignification treatments can improve saccharification, but they typically require large solvent inputs, resulting in environmental and economic burdens. Here, we present a green and facile Tween-assisted tartaric acid pretreatment that achieves both high yield of XOS and significantly enhanced enzymatic digestibility of birch. Under optimized conditions (0.4% tartaric acid, 0.5% Tween 80, 170 °C, 40 min), this process produced 43.2% XOS and enabled 77.7% glucose release from pretreated residues. Structural characterization revealed that Tween molecules etherify with lignin hydroxyl groups, reducing lignin hydrophobicity and enhancing cellulose accessibility of pretreated residues. Surface plasmon resonance, fluorescence quenching, and molecular docking analyses collectively confirmed that this in situ lignin modification mitigates the non-productive binding between enzyme and lignin, boosting enzymatic hydrolysis efficiency without an additional delignification step. This clean, low-cost, and scalable strategy effectively integrates the valorization of hemicellulose and cellulose in a single and sustainable process. Our study also offers molecular-level insights into surfactant-enabled lignin modification that could be widely deployed in the biorefining field.